Valve pad for inner tubes and process of making same



May 22, w23. 1,456,357

' l J. A. BOWERMAN VALVE PAD FOR INNER TUBES AND PROCESS OF MAKING SAME Filed NOV. l2 v1921 Y d I .W' Fl.

A ATToR Y llzatented May 22, lSZB.

l Ul S JSMH A. BOL" RUBBER, COMP i. MASSACHUSETTS.

f at? dll =v an, or wrrnnairaiu, MASSACHUSETTS, assrenon Terni-i risa or cnrcornn rams, Massacnuss, a conrpna'rron or 'VALVE P FOB INNER TUBES PROCESS OF-MING SE.

Applicationv iled November 42,1921. Serial. No. 514,717.

To aZZ 'whom it may cof/wcm:

Be it known that l, JOSEPH A. BOWERMAN, a citizen of the United States or America, residing at Wilbraham, in the county of Hampden and State of Massachusetts, have invented' certain new and usefulA improvements in a Valve Fad for lnner Tubes and Processes of Making Same, of which the following is a specification. My invention relates to the manufacture or a desired combination of rubber and fabric parts and particularly to the incorporation of valve 'pads in rubber articles such as inner-tubes for pneumatic tire casings.'

lit is one object of my invention toprovide a valve pad which isvsimple in 'construction and which can be quickl and eciently 1ncorporated with the rub er stock in formlil ing an inner tube. A more specific object of my invention is to provide a valve pad which can be incorporated in a rubber tube in such a manner as to obviate blowing or blistering in the rubber tube adjacent the nvalve pad during vulcanization. lt is also an object of my invention to' provide a new and useful method of making an inner tube having a valve pad vulcanized inthe tube in an improved manner. y

lt is customary to make inner tubes by mandrel and then vulcanizing the rub er while so wrapped upon the mandrel. ln order that the rubber tube may be reinforced at that portion through which the valve is .later to be positioned in the tube, it is necessary to provide within the tube a. valve *bad comprising several plies of rubberized fabric with their edges step edod'. Sometimes one or more plies ci ru ber are added to the valve pad. 'lh'is valve pad becomes incorporated with the tube during vulcanization and becomes a part thereof. According to the customary method of. construction ll have found that many tubes are spoiledduring blowing or blistering of the rubber' tube near the edge of the valve pad. l believe this condition is partly due to entrapped L air or ases caught between the severalV lies moisture in the fabric plies of the pad. 'lhs moisture turns into vapor during the heat of vulcanization. ile the rubber tube is in the process ot vulcanization the entrapped wrapping rubber stock about a strai htA vulcanization upon the mandrel because off: drei, a valve pad having a gasor vapor .con-v or stoc forming the valve pad and part y to air and vapor formedin the fabric plies of the valve pad and expanded by heat move to the edges of the pad laminations and frequently break through the rubber stock at one or more points, thus causing the blistering or blowing l have referred to. Accordinto my invention this result is avoided.

means of my invention l build inner tubes free of blow holes or blisters with the same ease as tubes have been built according to prior practice. The departure from theI usual practice, although sli ht, obviates aserious defect inherent in t e former practice. My invention will be described with reference to the accompanying drawin s; in which, i

i 1 is a plan Viewy partly broken away and indicating the rubberl stock just prior tio llieing rolled about a tube forming man re i Fig. 2 is a cross-section taken through the line Y2--2 of Fig. l showin in detail a vvalve pad having a hole throug its center;

Fig. 3 is another cross-section taken lthrough a valve pad having a hole through all but one of its laminations; Fig. d is a partial section taken through a tube forming mandrel upon which a rubber tube has been rolled, showin the oreferred form of valve pad which has a4 ole through only one fabric lamination;

Fig. 5 is 'a plan view of a valve pad;

Fig. 6 is a plan view of a segment of a' rubber tube which has been built according to the prior practice and which indicates a blown or blistered valve pad:

Fig. 7 is an inside view of the same; and

Fig. 8 is a plan view of a segment of a nislied rubber tube such as will be made by my invention, indicating the absence of blisters.

ln car ing out in invention l su l in combinathlin with theusual riibberppshlieet, which is to be ynioiinted upon a tube mantaining recess in one side thereof. The o ad is positioned u on the rubber slieetso tat the recess in the pad willrest against the mandrel after the combination has been mounted thereon. 'lhis arrangement forms a closed-pocket which will serve as an air or vapor containing means of sufficient capacity to hold in a harmless manner the entrapped air which Hows to it from between the valve pad laminations as well as the vapor generated in the valve pad during the vulcanization of the tube. it will be readily appreciated that as the air, gas or vapor in the valve pad laminations expand, their path of least resistance will be that path leading into the pocket (see Fig. 4) because the latter is within the pad and and the pad of fabric construction is more readily permeable by gas than the pure rubber stock of the tube.

The valve pads shown in cross-section in Figs. 2, 3 and 4 comprise a heavy ply of rubber stock 10 and three plies of rubberized fabric 12, 14 and 16 with their edges stepped od. In order to form an air or vapor containing recess 18, the purpose of which has already been described, an opening 2() is formed through the rubber ply 10 at approximately the center of that ply and openings 22 are formed through one or more of the fabric plies at approximately the center of those plies so as to form a recess of considerable size or suicient capacity for my purpose. rlhe size and shape of the recesses in the valve pads of the same size may vary from time to time, the main 'object being to form a pocket of suiicient capacity to harmlessly contain all the previously described gases and vapors expanded during the vulcanization of the rubber tube. The

openings 22 in the fabric plies are prefera bly cut therein after the fabric has been rubberized. ln this way the edges of the openin are formed by the unrubberized threads of the fabric and each thread serves as a convenient path of least resistance from the interior of the valve pad to the closed pocket between it and the mandrel.

In mounting this laminated valve pad in combination with the rubber sheet upon a tube vulcanizin mandrel, I place it upon the sheet 26 near t e edge 30 as shown in Figs. 1, 2 and 3. The recess 18 of the pad faces away from the sheet. The mandrel 28 is laid over the edge 30 of the sheet in the usual manner and the rubber is wra ped about the mandrel by rolling the mand)rel over it. The recess 18 by this means has its open end closed by the mandrel so as to form the pocket I have described. The mandrel is of usual form and any part of its surface will cooperate with recess 18 to form the desired pocket. The mounted combination is next vulcanized upon the mandrel and the valve pad becomes bodily incorporated in the rubber during such vulcanization. The closed pocket will receive and being of suicient capacity will hold the air, gas, or vapor in a harmless manner during vulcanization. When the tube has been vulcanized it is peeled oil" the mandrel by turning it inside out. The valve pad will then have the openings 20 and 22 upon the outside of the tube, and of course the gas or vapor will escape.

Maase? While the latter has been held within the valve pad during .vulcanization the final result is the same as if the gases had harmlessly escaped into the atmosphere during vulcanizati'on. rlhe means used to bring about the final result however is more convenient and economical than if direct venting means were used.

The blowing or blistering of the rubber tube around `the valve pad, which blowing or blistering occurs frequently in the former practice, is indicated in Figs. 6 and 7. Fig. 6 shows several blow holes 32 which have broken through to the outside of a rubber tube 3a around the valve pad 36 while Fig. 7 shows other blow-holes 32 which have broken through to the inside of the rubber tube.

My invention is capable of general application on straight or curved mandrels. In addition it contributes effectively to economy particularly where it is desired to vulcanize tubes with valve pads therein and avoid expensive forms of pressure applications to the tubes during vulcanization.

Having thus described my invention, l claim:

1. The method of making laminated articles of fabric and rubber which consists in forming a recess in the fabric, then laminating the fabric and rubber on a mandrel or mold surface with the recess closed by the latter, and vulcanizing.

2. The method of making laminated articles of fabric and rubber which consists in cutting a hole in rubberized fabric s0 as to leave the edges unrubberized, laminating the fabric and rubber layers on a mandrel or mold surface with the hole facing and closed at one end by such surface, and vulcanizing the article thus positioned.

3. In a method of making an inner tube the steps which consist in providing a vent pocket or recess in a laminated fabric valve f pad, applyin the valve pad and the unvulcanized ru ber tube on a mandrel for vulcanization with the vent pocket or recess completely closed, vulcanizing the pad and tube into a unit, and then opening the vent pocket.

4. In a method of making an inner tube, the steps which consist in cutting a hole at least partially through the rubberized fabric laminations of a valve ad so as to leave the edges of said hole unruberized, locating the valve pad between a mandrel and a surrounding imperforate unvulcanized tube, and vul-` canizing the tube and pad together.

5. In'a method of making an inner tube the steps which consist in providing in a laminated rubberized valve pad a vent pocket or recess having its fabric sides unrubberized, applying said pad and an 'unvulcanized tube to a mandrel with the vent pocket closed, but with the ends of the gas paths of small resistance along the fabric threads leading into the pocket,` and vuleanizing the two together.

6. In a method of making an inner tube, the steps which consist in cutting a hole in 5 the rubberized fabric laminatons of a valve pad so as to leave the edges of the hole unrubberized, building the pad into the unvulcanized rubber tube, locatingb the tube and pad together on a mandrel so that one end of the hole in the pad laminations is closed by the mandrel and the other by the tbe rubber, and vulcanizing the tube and pad together, whereby gases from the fabric lami nations are afforded a path into the pocket thus formed by the hole and are held there l5 harmlessly during vulcanization.

JOSEPH A. BOWERMAN. 

